Field of the Invention:
The invention relates to a process for producing an anode for electrochemical cells, in particular for solar cells, on conductive glass to which a layer of titanium dioxide is applied, the layer is then impregnated with metal complexes of the porphyrin-phthalocyanine class and/or other dyestuffs and then subjected to a heat treatment.
Published European Application No. 0 333 641 Al (corresponding to U.S. Pat. No. 4,927,721) discloses a process for producing a polycrystalline metal oxide semiconductor layer by the sol-gel method for a photoelectrochemical cell, wherein a titanium substrate made of pure titanium is first cleaned in boiling hydrochloric acid. A drop of a titanium ethoxide solution diluted with very pure methanol is applied to the substrate and then the titanium alkoxide is hydrolyzed at room temperature. Subsequently, the substrate with the hydrolyzed layer is heated for a short time at approximately 450.degree. C. That process is repeated several times. After it has been repeated 10 to 15 times, the titanium dioxide layer has reached about 20 .mu.m thickness. The substrate with the layer is then heat-treated at about 500.degree. C. in a pure argon atmosphere. A chromophore or dyestuff is then applied by immersing the substrate with the oxide layer in an aqueous solution of the particular dyestuff carrier for about 1 hour.
In carrying out the known process it is essential to exactly adhere to the specified, numerous parameters of the method, such as concentration, temperature, and duration, in order to achieve the desired result. In particular, according to the known process, the heat treatment of the titanium dioxide layer at 450.degree. to 500.degree. C. is necessary to consolidate the titanium dioxide layer. However, since the necessary dyestuffs are destroyed above 300.degree. C., according to the known process, the color is applied to the titanium dioxide layer at a low temperature, preferably room temperature. In that case, the dyestuff molecules are held on the surface of the titanium dioxide layer only by adsorptive mechanisms.
As is evident from the process cycle explained above, the known process for producing photoelectrochemical cells, in particular for use as solar cells, requires a considerable expenditure. In particular, the long time requirement for the preparation of the titanium substrate for the formation of a titanium dioxide layer makes the known process unattractive for an economic application since the costs to be expended thereon are disproportionate to the achievable result.